1. Field of the Invention
The present invention relates to a gear apparatus suitable for use in a power transmission apparatus for automotive vehicle, and more specifically to a gear apparatus small in size, long in life time, and excellent in lubrication.
2. Description of the Prior Art
An example of prior-art gear apparatus is disclosed in Japanese Published Unexamined Patent Appli. No. 58-63523, as shown in FIG. 1. In this prior-art gear apparatus, engine power is first applied to a center differential gear 101, and then transmitted to right and left front wheel drive shafts 109 and 111 via a front differential gear 107, and further to a propeller shaft via two bevel gears 123 and 125. In more detail with reference to FIG. 1, an engine power is transmitted from a transmission (not shown) to the center differential gear 101 to differentially drive two front wheel drive shafts 109 and 111 and a propeller shaft. When a first side gear 103 of the center differential gear 101 is driven, engine power is transmitted to the front differential gear 107 via a first hollow drive shaft 105 to differentially drive the right and left front wheel drive shafts 109 and 111. On the other hand, when a second side gear 113 of the center differential gear 101 is driven, engine power is transmitted to a propeller shaft (not shown) to drive the rear wheel drive shafts by way of a second hollow drive shaft 115, a large-diameter transmission gear 117 spline engaged with the second hollow drive shaft 115, a small-diameter transmission gear 119 in mesh with the large-diameter transmission gear 117, an intermediate shaft 121 spline engaged with the small-diameter transmission gear 119, a first bevel gear 123 spline engaged with the intermediate shaft 121, and a second bevel gear 125 fixed to a drive pinion shaft in mesh with the first bevel gear 123. In the prior-art gear apparatus as shown in FIG. 1, the first bevel gear 123 and the intermediate shaft 121 are rotatably supported within a transfer case 131 via two opposingly disposed bearings 127 and 129. In this prior-art supporting structure, however, since the two opposing bearings 127 and 129 must be arranged outside the two bevel gears 123 and 125 and the small-diameter transmission gear 119, there exist various problems in that the distance between the two bearings is long; a radial load applied to the intermediate shaft 121 is not uniformly supported by the two bearings, so that the gear apparatus inevitably increases in size and decreases in life time. In addition, since the left side bearing 127 is located on the left side of the first bevel gear 123 within the transfer case 131, there exists another problem in that the bearing 127 is not sufficiently lubricated by lubricant put in the transfer case 131 and scattered by the rotation of the bevel gears 123 and 125 arranged within the transfer case 131.